Process for total treatment of copper-containing iron pyrites



p 29, 1953 s. A. AANNERUD 2,653,905

PROCESS FOR TOTAL TREATMENT OF COPPER-CONTAINING IRON PYRITES Filed Nov.22, 1948 Pyrite 1 (Fe 52 m.)

Fe Setc. Hz 804 Sludge Fe 504 '(Fe,Cu,S+ Ouartz etc.)

Slag (Fe 0,8i 02) INVENTOR SIGURD ARTHUR AANNERUD TouJZ/rm'm. 5iTuubmixv ATTORNEYS Patented Sept. 29, 1953 PROCESS FOR TOTAL TREATMENTOF COPPER-CONTAINING IRON PYRITES Sigurd Arthur Aannerud, Thamshavn,Norway,

assignor, by. memo assignments, to Pyror Limited, Pembroke, Bermuda, acorporation of Bermuda Application November 22, 1948; Serial No. 61,376

According to several methods heretofore known of treatingcopper-containing iron pyrites, the sulphur content of the ore isrecovered as elementary sulphur and the copper content in the form ofcopper or copper matte. To this end, the recovery of elementary sulphuris effected by the use of reducing agents such as coke or, if desired,carbon monoxide for the reduction of S02 produced by total or partialroasting of the pyrites. Apart from the fact that thereby a largequantity of fuel is consumed, the iron content of the ore and othermetals which in addition to the copper may be present in smallquantities, are often not utilized. In addition, when roasting with air,the S02 gas is not obtained in pure form, but mixed with theconstituents of the air, for which reason an absorption of S02 from theroast gases is often effected before the reduction process. 7

It is an object of the present invention to provide a process wherebythe sulphur content of the ore may be recovered as elementary sulphur bythe use of reactions known per se without requiring coke or otherreducing agents for the main reaction. It is another object of thisinvention to provide a method as set forth in the preceding paragraph,which will make it possible to utilize substantially the whole mineralcontent of the ore to obtain pure sulphur-containing gases.

These and other objects and advantages of the invention will appear moreclearly from the following description in connection with theaccompanying drawing, which shows a flow sheet for the course of theprocess according to the invention.

The iron pyrites are first heated in preferably continuously charged,closed furnaces indicated by the reference numeral l, to a temperaturewhereby one sulphur atom is driven off. The heating may take place incountercurrent to a suitable heating medium either indirectly by meansof muffles or the like, or directly with an inert circulating gas.However, care is taken that the ore does not attain a temperature ofabout 1009 centigrades at which the sintering begins, and preferably theoperation takes place with a maximum temperature up to 900- centigrades.

The escaping sulphur may be condensed in the usual manner by cooling insteam boilers (indicated at 2 in the drawing), thereby utilizing thecondensation heat,

Owing to the driving 01? of the first sulphur atom without sintering,the ore thus treated, which now contains FeS and sulphides of copper andof other metals which may be present,

Norway Decemberfi, 1947 '4 Claims. (01.204-112).

and quartz, is now in an entirely porous, solid form, which makes itparticularly suitedfor a treatment with chemicals- In this form it issupplied to containers 3 in which it is treated with sulphuric acidwhich may be used in a low concentration down to about 5%. By thistreatment the major part of the iron is dissolved, while a correspondingproportion of sulphur is driven off as sulphurated hydrogen. Thisprocess can be carried out at usual temperature, but in order that itshall proceed more rapidly, it is convenient to keep a somewhat highertemperature of for example 90 centigrades, utilizing part of the heatcontent of the ore from the first step of treatment. It has been foundthat the dissolution can be carried on in a fractional manner, that is,that it is possible to dissolve most of the iron without dissolving thecopper, which remains in the solid residue.

The iron sulphate formed is, supplied to electrolysers 4 equipped with asuitable diaphragm for the electrolytic separation of the iron, ifdetreatment may for example take place by means of the Claus-process(catalytic combustion HzS-eO I-I2O+S), but a procedure is preferred inwhich a minor part of the sulphurated hydrogen gas is burntso as to formsoziindicated by 5), using preferably oxygen from the elec trolysis asindicated above (if the combustion is efiected with air, the sulphurdioxide may in known manner be absorbed in a suitable absorbing agentand driven off again as -percentual) whereafter the remainingsulphurated hydrogen gas is mixed with the sulphur dioxide in the volumeratio 2:1 and passed over a suitable catalyser (at 6) whereby thefollowing reaction is obtained at a suitable temperature Flor thisprocess it is possible for example to use porous alumina-containingcatalyser mass in known manner, Since by this process it is possible toobtain the sulphur in liquid form and H20 in the form of steam, thesulphur may without difficulty be collected separately. And as theprocess may take place together with a reduction of the gas volume, itmay be accelerated by the application of pressure. Thus, additionally,

3 the H20 formed is obtained in the form of pressure steam which can beutilized for example for driving pressure pumps for the gas to beintroduced.

In the residue from the acid treatment the copper remains together withthe silica and some iron and sulphur apart from valuable metals whichmay be contained in the ore, such as gold, silver and cobalt. This richcopper sludge may be treated by known methods for recovering the copperand other valuable constituents for example by direct melting andBessemer treatment or roasting and extraction, if desired combined witha flotation. As shown in the drawing, in which this treatment isindicated by 1, it is possible also for this roasting to use pure oxygenfrom the electrolysis and to have the remainder of the sulphur recoveredby mixing the sulphur dioxide formed by the roasting, with the gas fromthe combustion of HzS, which is conveyed to the catalyzing step. Themeasuring of oxygen and sulphurated hydrogen to the various steps of theprocess will in that case be made by means of gasometres in such amanner that the correct mixing ratio 2:1 is obtained for the catalysis.

I claim:

1. A process of treating an iron ore comprising sulphur and containingvaluable metal constituents including copper, which includes the stepsof (a) heating the ore under non-oxidizing conditions to a temperaturebelow sintering temperatures of the ore so as to decompose said ore andproduce gaseous sulphur, leaving a porous calcined product withsubstantially all of the original FeSz present reduced to FeS, (b)dissolving the major part of the iron content of said calcined productselectively by leaching fractional portions of said calcined productwith dilute sulphuric acid solution, leaving undissolved the major partof the copper and other of said valuable metal constituents presentforming a resultant mixture comprising ferrous sulphate solution,gaseous hydrogen sulphide, and a sludge containing undissolved solidmatter, and (c) electrolyzing said ferrous sulphate solution in adiaphragm electrolytic cell to electrolytically recover metallic ironand sulphuric acid and gaseous oxygen, (d) subjecting said sludge to aroasting treatment with oxygen recovered by step (c) to produce gaseoussulphur dioxide and effect recovery of said valuable metal constituents,and (e) reacting said sulphur dioxide with gaseous hydrogen sulphidefrom said mixture in the presence of a catalyst for forming liquidsulphur and steam.

2. A process of treating an iron ore comprising sulphur and containingvaluable metals including copper, which includes the steps of (a)heating the ore under non-oxidizing conditions to a temperature belowthat at which said ore sinters but high enough to decompose the ore andproduce gaseous sulphur, leaving a porous calcined product with theoriginal FeSz substantially reduced to FeS, (b) dissolving the majorpart of the iron content of said calcined product selectively byleaching fractional portions of said calcined product with dilutesulphuric acid solution leaving undissolved the major part of the copperand other of said valuable metal components present forming a resultantmixture comprising ferrous sulphate solution, gaseous hydrogen sulphide,and a sludge containing undissolved solid matter, (c) electrolyzing saidferrous sulphate solution in a diaphragm electrolytic cell forelectrolytically separating and obtaining sulphuric acid, metallic ironand gaseous oxygen, and (d) subjecting said sludge to a roastingtreatment with the oxygen thus obtained to recover said valuable metalconstituents from said roasted sludge.

3. A process of treating an iron ore comprising sulphur and containingvaluable metals including copper, which comprises the steps of heatingthe ore under non-oxidizing conditions to a temperature .below that atwhich said ore sinters but high enough to produce gaseous sulphur whileleaving a porous calcined product with the original FeSz substantiallyreduced to FeS; dissolving the major part of the iron content of saidcalcined product selectively by leaching said product in fractionalportions with dilute sulphuric acid solution, leaving undissolved themajor part of the copper and other of said valuable metal componentspresent producing ferrous sulphate solution, gaseous hydrogen sulphide,and a sludge containing undissolved solid matter; electrolyzing saidferrous sulphate solution in a diaphragm electrolytic cell for obtainingsulphuric acid, metallic iron and gaseous oxygen; reacting a part ofsaid gaseous hydrogen sulphide with said oxygen thus recovered toproduce sulphur dioxide; and reacting said sulphur dioxide with furtheramounts of said hydrogen sulphide in the presence of a catalyst forforming liquid sulphur and steam.

4. A process for treating an iron ore comprising sulphur and containingvaluable metals including copper, which comprises the steps of heatingthe ore under non-oxidizing conditions to a temperature below that atwhich said ore sinters but high enough to decompose said ore and producegaseous sulphur and leaving a porous calcined product containing theoriginal Fess substantially all reduced to FcS; dissolving the majorpart of the iron content of said calcine selectively by leachingfractional portions of said calcine with dilute sulphuric acid solutionleaving undissolved the major part of the copper and other of saidvaluable components present to produce a resultant mixture comprisingferrous sulphate solution, gaseous hydrogen sulphide, and a sludgecontaining undissolved solid matter; electrolyzing said ferrous sulphatesolution in a diaphragm electrolytic cell for recovering sulphuric acid,metallic iron and gaseous oxygen; burning a part of said gaseoushydrogen sulphide with a part of said oxygen; subjecting said sludge toa roasting treatment with a portion of said oxygen, for recovering saidvaluable metal constituents therefrom; and reacting sulphur dioxide,formed by said burning and by said roasting, with another portion ofsaid gaseous hydrogen sulphide in the presence of a catalyst and incontrolled proportions so as to produce liquid sulphur and steam.

SIGURD ARTHUR AAN N ERUD.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 748,662 Sebillot Jan. 5, 1904 814,049 Johnson Mar. 6, 1906984,703 Ramage Feb. 2l, 1911 1,083,250 Hall Dec. 30, 1913 1,378,145Stuclt May 17, 1921 1,565,353 Estelle Dec. 15, 1925 1,602,795 GreenawaltOct. 12, 1926 1,633,091 Greenawalt June 21, 1927 1,654,930 GreenawaltJan. 3, 1928

1. A PROCESS OF TREATING AN IRON ORE COMPRISING SULPHUR AND CONTAININGVALUABLE METAL CONSTITUENTS INCLUDING COPPER, WHICH INCLUDES THE STEPSOF (A) HEATING THE ORE UNDER NON-OXIDIZING CONDITIONS TO A TEMPERATUREBELOW SINTERIN TEMPERATURES OF THE ORE SO AS TO DECOMPOSE SAID ORE ANDPRODUCE GAEOUS SULPHUR, LEAVING A POROUS CALCINED PRODUCT WITHSUBSTANTIALLY ALL OF THE ORIGINAL FES2 PRESENT REDUCED TO FES, (B)DISSOLVING THE MAJOR PART OF TH IRON CONTENT OF SAID CALCINED PRODUCTSELECTIVELY BE LEACHING FRACTIONAL PORTIONS OF SAID CALCINED PRODUCTWITH DILUTE SULPHURIC ACID SOLUTION, LEAVING UNDISSOLVED THE MAJOR PARTOF THE COPPEER AND OTHER OF SAID VALUABLE MIXTURE COMPRISING FERROUSSULING A RESULTANT MIXTURE COMPRISING FERROUS SUL PHATE SOLUTION,GASEOUS HYDROGEN SULPHIDE, AND A SLUDGE CONTAINING UNDISSOLVED SOLIDMATTER, AND (C) TO PRODUCE GASEOUS SULPHUR DIOXIDE AND EFFECT RECOVERYOF SAID VALUABLE METAL CONSTITUENTS, AND RECOVER METALLIC IRON ANDSULPHURIC ACID AND GASEOUS OXYGEN, (D) SUBJECTING SAID SLUDGE TO AROASTING TREATMENT WITH OXYGEN DIOXIDE BY STEP (C) TO PRODUCT GASEOUSSULPHR DIOXIDE AND EFFECT RECOVERY OF SAID VALUABLE METAL CONSTITUENTS,AND (E) REACTING SAID SULPHUR DIOXIDE WITH GASEOUS HYDROGEN SULPHIDEFROM SAID MIXURE IN THE PRESENCE OF A CATALYST FOR FORMING LIQUIDSULPHUR AND STEAM.